The result is all the more important as astronomers have used galaxies such as Leo I, called “dwarf spheroidal galaxies,” for 20 years to understand how dark matter is distributed within galaxies, Gebhardt added. This new type of black hole merger also gives gravitational wave observatories a new signal to search for. The finding could shake up astronomers’ understanding of galaxy evolution, as “there is no explanation for this kind of black hole in dwarf spheroidal galaxies,” Bustamante said. The amount of inferred matter enclosed within the stars’ orbits skyrocketed.

The new data is concentrated in the central region and is unaffected by this bias. Credit: Marty Harris/McDonald Observatory Smith Telescope at The University of Texas at Austin McDonald Observatory. This, in turn, decreased the inferred amount of matter enclosed within their orbits. The current study showed that for those few velocities that were taken in the past, there was a bias toward low velocities. The central, dense region of the galaxy was mostly unexplored in previous studies, which concentrated on the velocities of individual stars. The researchers said the result was different from the past studies of Leo I due to a combination of better data and the supercomputer simulations. The Milky Way is dominant the Leo I black hole is almost comparable.” The result is unprecedented. “You have a very small galaxy that is falling into the Milky Way, and its black hole is about as massive as the Milky Way’s. “The models are screaming that you need a black hole at the center you don’t really need a lot of dark matter,” Gebhardt said.

When the team fed their improved data and sophisticated models into a supercomputer at UT Austin’s Texas Advanced Computing Center, they got a startling result. Led by recent UT Austin doctoral graduate María José Bustamante, the team includes UT astronomers Eva Noyola, Karl Gebhardt and Greg Zeimann, as well as colleagues from Germany’s Max Planck Institute for Extraterrestrial Physics (MPE).įor their observations, they used a unique instrument called VIRUS-W on McDonald Observatory’s 2.7-meter Harlan J. The result could signal changes in astronomers’ understanding of galaxy evolution. Leo I is 30 times smaller than the Milky Way. McDonald Observatory astronomers have found that Leo I (inset), a tiny satellite galaxy of the Milky Way (main image), has a black hole nearly as massive as the Milky Way’s. They also wanted to know whether their profile measurement would match previous ones made using older telescope data combined with computer models. In particular, the team wanted to know whether dark matter density increases toward the galaxy’s center. They did this by measuring its gravitational pull on the stars: The faster the stars are moving, the more matter there is enclosed in their orbits. Researchers measured Leo I’s dark matter profile - that is, how the density of dark matter changes from the outer edges of the galaxy all the way into its center. Unlike most dwarf galaxies orbiting the Milky Way, Leo I does not contain much dark matter.

The team decided to study Leo I because of its peculiarity. The work is published in a recent issue of The Astrophysical Journal. Almost as massive as the black hole in our own galaxy, the finding could redefine our understanding of how all galaxies - the building blocks of the universe - evolve. Astronomers at The University of Texas at Austin’s McDonald Observatory have discovered an unusually massive black hole at the heart of one of the Milky Way’s dwarf satellite galaxies, called Leo I.

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